Long Term Evolution (LTE)
Third-generation mobile systems (3G) based on WCDMA radio-access technology are being deployed on a broad scale all around the world. A first step in enhancing or evolving this technology entails introducing High-Speed Downlink Packet Access (HSDPA) and an enhanced uplink, also referred to as High Speed Uplink Packet Access (HSUPA), giving a radio access technology that is highly competitive.
In order to be prepared for further increasing user demands and to be competitive against new radio access technologies, 3GPP introduced a new mobile communication system which is called Long Term Evolution (LTE). LTE is designed to meet the carrier needs for high speed data and media transport as well as high capacity voice support for the next decade. The ability to provide high bit rates is a key measure for LTE.
The work item (WI) specification on Long-Term Evolution (LTE) called Evolved UMTS Terrestrial Radio Access (UTRA) and UMTS Terrestrial Radio Access Network (UTRAN) is finalized as Release 8 (LTE Rel. 8). The LTE system represents efficient packet-based radio access and radio access networks that provide full IP-based functionalities with low latency and low cost. In LTE, scalable multiple transmission bandwidths are specified such as 1.4, 3.0, 5.0, 10.0, 15.0, and 20.0 MHz, in order to achieve flexible system deployment using a given spectrum. In the downlink, Orthogonal Frequency Division Multiplexing (OFDM) based radio access was adopted because of its inherent immunity to multipath interference (MPI) due to a low symbol rate, the use of a cyclic prefix (CP) and its affinity to different transmission bandwidth arrangements. Single-carrier frequency division multiple access (SC-FDMA) based radio access was adopted in the uplink, since provisioning of wide area coverage was prioritized over improvement in the peak data rate considering the restricted transmit power of the user equipment (UE). Many key packet radio access techniques are employed including multiple-input multiple-output (MIMO) channel transmission techniques and a highly efficient control signaling structure is achieved in LTE Rel. 8/9.
LTE Architecture
The overall architecture is shown in FIG. 1 and a more detailed representation of the E-UTRAN architecture is given in FIG. 2. The E-UTRAN consists of an eNodeB, providing the E-UTRA user plane (PDCP/RLC/MAC/PHY) and control plane (RRC) protocol terminations towards the user equipment (UE). The eNodeB (eNB) hosts the Physical (PHY), Medium Access Control (MAC), Radio Link Control (RLC) and Packet Data Control Protocol (PDCP) layers that include the functionality of user-plane header-compression and encryption. It also offers Radio Resource Control (RRC) functionality corresponding to the control plane. It performs many functions including radio resource management, admission control, scheduling, enforcement of negotiated uplink Quality of Service (QoS), cell information broadcast, ciphering/deciphering of user and control plane data, and compression/decompression of downlink/uplink user plane packet headers. The eNodeBs are interconnected with each other by means of the X2 interface.
The eNodeBs are also connected by means of the S1 interface to the EPC (Evolved Packet Core), more specifically to the MME (Mobility Management Entity) by means of the S1-MME and to the Serving Gateway (SGW) by means of the S1-U. The S1 interface supports a many-to-many relation between MMEs/Serving Gateways and eNodeBs. The SGW routes and forwards user data packets, while also acting as the mobility anchor for the user plane during inter-eNodeB handovers and as the anchor for mobility between LTE and other 3GPP technologies (terminating S4 interface and relaying the traffic between 2G/3G systems and PDN GW). For idle state user equipments, the SGW terminates the downlink data path and triggers paging when downlink data arrives for the user equipment. It manages and stores user equipment contexts, e.g. parameters of the IP bearer service, network internal routing information. It also performs replication of the user traffic in case of lawful interception.
The MME is the key control-node for the LTE access-network. It is responsible for idle mode user equipment tracking and paging procedure including retransmissions. It is involved in the bearer activation/deactivation process and is also responsible for choosing the SGW for a user equipment at the initial attach and at time of intra-LTE handover involving Core Network (CN) node relocation. It is responsible for authenticating the user (by interacting with the HSS). The Non-Access Stratum (NAS) signaling terminates at the MME and it is also responsible for generation and allocation of temporary identities to user equipments. It checks the authorization of the user equipment to camp on the service provider's Public Land Mobile Network (PLMN) and enforces user equipment roaming restrictions. The MME is the termination point in the network for ciphering/integrity protection for NAS signaling and handles the security key management. Lawful interception of signaling is also supported by the MME. The MME also provides the control plane function for mobility between LTE and 2G/3G access networks with the S3 interface terminating at the MME from the SGSN. The MME also terminates the S6a interface towards the home HSS for roaming user equipments.
Component Carrier Structure in LTE (Release 8)
The downlink component carrier of a 3GPP LTE (Release 8 and further) is subdivided in the time-frequency domain in so-called subframes. In 3GPP LTE (Release 8 and further) each subframe is divided into two downlink slots as shown in FIG. 3, wherein the first downlink slot comprises the control channel region (PDCCH region) within the first OFDM symbols. Each subframe consists of a give number of OFDM symbols in the time domain (12 or 14 OFDM symbols in 3GPP LTE, Release 8 and further), wherein each OFDM symbol spans over the entire bandwidth of the component carrier. The OFDM symbols thus each consists of a number of modulation symbols transmitted on respective NRBDL×NscRB subcarriers as also shown in FIG. 4.
Assuming a multi-carrier communication system, e.g. employing OFDM, as for example used in 3GPP Long Term Evolution (LTE), the smallest unit of resources that can be assigned by the scheduler is one “resource block”. A physical resource block (PRB) is defined as NsymbDL consecutive OFDM symbols in the time domain (e.g. 7 OFDM symbols) and NscRB consecutive subcarriers in the frequency domain as exemplified in FIG. 4 (e.g. 12 subcarriers for a component carrier). In 3GPP LTE (Release 8), a physical resource block thus consists of NsymbDL×NscRB resource elements, corresponding to one slot in the time domain and 180 kHz in the frequency domain (for further details on the downlink resource grid, see for example 3GPP TS 36.211, “Evolved Universal Terrestrial Radio Access (E-UTRA); Physical Channels and Modulation (Release 8)”, section 6.2, available at http://www.3gpp.org and incorporated herein by reference).
One subframe consists of two slots, so that there are 14 OFDM symbols in a subframe when a so-called “normal” CP (cyclic prefix) is used, and 12 OFDM symbols in a subframe when a so-called “extended” CP is used. For sake of terminology, in the following the time-frequency resources equivalent to the same NscRB consecutive subcarriers spanning a full subframe is called a “resource block pair”, or equivalent “RB pair” or “PRB pair”.
The term “component carrier” refers to a combination of several resource blocks in the frequency domain. In future releases of LTE, the term “component carrier” is no longer used; instead, the terminology is changed to “cell”, which refers to a combination of downlink and optionally uplink resources. The linking between the carrier frequency of the downlink resources and the carrier frequency of the uplink resources is indicated in the system information transmitted on the downlink resources.
Similar assumptions for the component carrier structure apply to later releases too.
Logical and Transport Channels
The MAC layer provides a data transfer service for the RLC layer through logical channels. Logical channels are either Control Logical Channels which carry control data such as RRC signalling, or Traffic Logical Channels which carry user plane data. Broadcast Control Channel (BCCH), Paging Control channel (PCCH), Common Control Channel (CCCH), Multicast Control Channel (MCCH) and Dedicated Control Channel (DCCH) are Control Logical Channels. Dedicated Traffic channel (DTCH) and Multicast Traffic Channel (MTCH) are Traffic Logical Channels.
Data from the MAC layer is exchanged with the physical layer through Transport Channels. Data is multiplexed into transport channels depending on how it is transmitted over the air. Transport channels are classified as downlink or uplink as follows. Broadcast Channel (BCH), Downlink Shared Channel (DL-SCH), Paging Channel (PCH) and Multicast Channel (MCH) are downlink transport channels, whereas the Uplink Shared Channel (UL-SCH) and the Random Access Channel (RACH) are uplink transport channels.
A multiplexing is then performed between logical channels and transport channels in the downlink and uplink respectively.
Layer 1/Layer 2 (L1/L2) Control Signaling
In order to inform the scheduled users about their allocation status, transport format and other data-related information (e.g. HARQ information, transmit power control (TPC) commands), L1/L2 control signaling is transmitted on the downlink along with the data. L1/L2 control signaling is multiplexed with the downlink data in a subframe, assuming that the user allocation can change from subframe to subframe. It should be noted that user allocation might also be performed on a TTI (Transmission Time Interval) basis, where the TTI length can be a multiple of the subframes. The TTI length may be fixed in a service area for all users, may be different for different users, or may even by dynamic for each user. Generally, the L1/2 control signaling needs only be transmitted once per TTI. Without loss of generality, the following assumes that a TTI is equivalent to one subframe.
The L1/L2 control signaling is transmitted on the Physical Downlink Control Channel (PDCCH). A PDCCH carries a message as a Downlink Control Information (DCI), which in most cases includes resource assignments and other control information for a mobile terminal or groups of UEs. In general, several PDCCHs can be transmitted in one subframe.
It should be noted that in 3GPP LTE, assignments for uplink data transmissions, also referred to as uplink scheduling grants or uplink resource assignments, are also transmitted on the PDCCH.
Generally, the information sent on the L1/L2 control signaling for assigning uplink or downlink radio resources (particularly LTE(−A) Release 10) can be categorized to the following items:
User identity, indicating the user that is allocated. This is typically included in the checksum by masking the CRC with the user identity;
Resource allocation information, indicating the resources (Resource Blocks, RBs) on which a user is allocated. Note, that the number of RBs on which a user is allocated can be dynamic;
Carrier indicator, which is used if a control channel transmitted on a first carrier assigns resources that concern a second carrier, i.e. resources on a second carrier or resources related to a second carrier;
Modulation and coding scheme that determines the employed modulation scheme and coding rate;
HARQ information, such as a new data indicator (NDI) and/or a redundancy version (RV) that is particularly useful in retransmissions of data packets or parts thereof;
Power control commands to adjust the transmit power of the assigned uplink data or control information transmission;
Reference signal information such as the applied cyclic shift and/or orthogonal cover code index, which are to be employed for transmission or reception of reference signals related to the assignment;
Uplink or downlink assignment index that is used to identify an order of assignments, which is particularly useful in TDD systems;
Hopping information, e.g. an indication whether and how to apply resource hopping in order to increase the frequency diversity;
CSI request, which is used to trigger the transmission of channel state information in an assigned resource; and
Multi-cluster information, which is a flag used to indicate and control whether the transmission occurs in a single cluster (contiguous set of RBs) or in multiple clusters (at least two non-contiguous sets of contiguous RBs). Multi-cluster allocation has been introduced by 3GPP LTE-(A) Release 10.
It is to be noted that the above listing is non-exhaustive, and not all mentioned information items need to be present in each PDCCH transmission depending on the DCI format that is used.
Downlink control information occurs in several formats that differ in overall size and also in the information contained in its fields. The different DCI formats that are currently defined for LTE are as follows and described in detail in 3GPP TS 36.212, “Multiplexing and channel coding”, section 5.3.3.1 (available at http://www.3gpp.org and incorporated herein by reference). For further information regarding the DCI formats and the particular information that is transmitted in the DCI, please refer to the technical standard or to LTE—The UMTS Long Term Evolution—From Theory to Practice, Edited by Stefanie Sesia, Issam Toufik, Matthew Baker, Chapter 9.3, incorporated herein by reference.
Format 0: DCI Format 0 is used for the transmission of resource grants for the PUSCH, using single-antenna port transmissions in uplink transmission mode 1 or 2.
Format 1: DCI Format 1 is used for the transmission of resource assignments for single codeword PDSCH transmissions (downlink transmission modes 1, 2 and 7).
Format 1A: DCI Format 1A is used for compact signaling of resource assignments for single codeword PDSCH transmissions, and for allocating a dedicated preamble signature to a mobile terminal for contention-free random access.
Format 1 B: DCI Format 1B is used for compact signaling of resource assignments for PDSCH transmissions using closed loop precoding with rank-1 transmission (downlink transmission mode 6). The information transmitted is the same as in Format 1A, but with the addition of an indicator of the precoding vector applied for the PDSCH transmission.
Format 1C: DCI Format 1C is used for very compact transmission of PDSCH assignments. When format 1C is used, the PDSCH transmission is constrained to using QPSK modulation. This is used, for example, for signaling paging messages and broadcast system information messages.
Format 1 D: DCI Format 1D is used for compact signaling of resource assignments for PDSCH transmission using multi-user MIMO. The information transmitted is the same as in Format 1B, but instead of one of the bits of the precoding vector indicators, there is a single bit to indicate whether a power offset is applied to the data symbols. This feature is needed to show whether or not the transmission power is shared between two UEs. Future versions of LTE may extend this to the case of power sharing between larger numbers of UEs.
Format 2: DCI Format 2 is used for the transmission of resource assignments for PDSCH for closed-loop MIMO operation.
Format 2A: DCI Format 2A is used for the transmission of resource assignments for PDSCH for open-loop MIMO operation. The information transmitted is the same as for Format 2, except that if the eNodeB has two transmit antenna ports, there is no precoding information, and for four antenna ports two bits are used to indicate the transmission rank.
Format 2B: Introduced in Release 9 and is used for the transmission of resource assignments for PDSCH for dual-layer beamforming.
Format 2C: Introduced in Release 10 and is used for the transmission of resource assignments for PDSCH for closed-loop single-user or multi-user MIMO operation with up to 8 layers.
Format 2D: introduced in Release 11 and is used for up to 8 layer transmissions; mainly used for COMP (Cooperative Multipoint)
Format 3 and 3A: DCI formats 3 and 3A are used for the transmission of power control commands for PUCCH and PUSCH with 2-bit or 1-bit power adjustments respectively. These DCI formats contain individual power control commands for a group of UEs.
Format 4: DCI format 4 is used for the scheduling of the PUSCH, using closed-loop spatial multiplexing transmissions in uplink transmission mode 2.
The following table gives an overview of some available DCI formats and the typical number of bits, assuming for illustration purposes a system bandwidth of 50 RBs and four antennas at the eNodeB. The number of bits indicated in the right column include the bits for the CRC of the particular DCI.
TABLEDCI FormatsNumberof bitsDCIincludingformatPurposeCRC0PUSCH grants431PDSCH assignments with a single codeword471APDSCH assignments using a compact format431BPDSCH assignments for rank-1 transmission461CPDSCH assignments using a very compact format291DPDSCH assignments for multi-user MIMO462PDSCH assignments for closed-loop MIMO62operation2APDSCH assignments for open-loop MIMO operation582BPDSCH assignments for dual-layer beamforming572CPDSCH assignments for closed-loop single-user or58multiuser MIMO operation2DPDSCH assignments for closed-loop single-user or61multi-user MIMO operation, COMP3Transmit Power Control (TPC) commands for43multiple users for PUCCH and PUSCH with 2-bitpower adjustments3ATransmit Power Control (TPC) commands for43multiple users for PUCCH and PUSCH with 1-bitpower adjustments4PUSCH grants52
In order for the UE to identify whether it has received a PDCCH transmission correctly, error detection is provided by means of a 16-bit CRC appended to each PDCCH (i.e. DCI). Furthermore, it is necessary that the UE can identify which PDCCH(s) are intended for it. This could in theory be achieved by adding an identifier to the PDCCH payload; however, it turns out to be more efficient to scramble the CRC with the “UE identity”, which saves the additional overhead. The CRC may be calculated and scrambled as defined in detail by 3GPP in TS 36.212, Section 5.3.3.2 “CRC attachment”, incorporated hereby by reference. The section describes how error detection is provided on DCI transmissions through a Cyclic Redundancy Check (CRC). A brief summary is given below.
The entire payload is used to calculate the CRC parity bits. The parity bits are computed and attached. In the case where UE transmit antenna selection is not configured or applicable, after attachment, the CRC parity bits are scrambled with the corresponding RNTI.
The scrambling may further depend on the UE transmit antenna selection, as apparent from TS 36.212. In the case where UE transmit antenna selection is configured and applicable, after attachment, the CRC parity bits are scrambled with an antenna selection mask and the corresponding RNTI. As in both cases the RNTI is involved in the scrambling operation, for simplicity and without loss of generality the following description of the embodiments simply refers to the CRC being scrambled (and descrambled, as applicable) with an RNTI, which should therefore be understood as notwithstanding e.g. a further element in the scrambling process such as an antenna selection mask.
Correspondingly, the UE descrambles the CRC by applying the “UE identity” and, if no CRC error is detected, the UE determines that PDCCH carries its control information intended for itself. The terminology of “masking” and “de-masking” is used as well, for the above-described process of scrambling a CRC with an identity.
The “UE identity” mentioned above with which the CRC of the DCI may be scrambled can also be a SI-RNTI (System Information Radio Network Temporary Identifier), which is not a “UE identity” as such, but rather an identifier associated with the type of information that is indicated and transmitted, in this case the system information. The SI-RNTI is usually fixed in the specification and thus known a priori to all UEs.
There are various types of RNTIs that are used for different purposes. The following tables taken from 3GPP 36.321 Chapter 7.1 shall give an overview of the various 16-bits RNTIs and their usages.
TABLERNTIsValue(hexa-decimal)RNTI0000N/A0001-003CRA-RNTI, C-RNTI, Semi-Persistent SchedulingC-RNTI, Temporary C-RNTI, TPC-PUCCH-RNTIand TPC-PUSCH-RNTI (see note)003D-FFF3C-RNTI, Semi-Persistent Scheduling C-RNTI,Temporary C-RNTI, TPC-PUCCH-RNTI andTPC-PUSCH-RNTIFFF4-FFFCReserved for future useFFFDM-RNTIFFFEP-RNTIFFFFSI-RNTIPhysical Downlink Control Channel (PDCCH) and Physical Downlink Shared Channel (PDSCH)
The physical downlink control channel (PDCCH) carries e.g. scheduling grants for allocating resources for downlink or uplink data transmission. Multiple PDCCHs can be transmitted in a subframe.
The PDCCH for the user equipments is transmitted on the first NsymbPDCCH OFDM symbols (usually either 1, 2 or 3 OFDM symbols as indicated by the PCFICH, in exceptional cases either 2, 3, or 4 OFDM symbols as indicated by the PCFICH) within a subframe, extending over the entire system bandwidth; the system bandwidth is typically equivalent to the span of a cell or component carrier. The region occupied by the first NsymbPDCCH OFDM symbols in the time domain and the NRBDL×NscRB, subcarriers in the frequency domain is also referred to as PDCCH region or control channel region. The remaining NsymbPDSCH=2·NsymbDL−NsymbPDCCH OFDM symbols in the time domain on the NRBDL×NscRB subcarriers in the frequency domain is referred to as the PDSCH region or shared channel region (see below).
For a downlink grant (i.e. resource assignment) on the physical downlink shared channel (PDSCH), the PDCCH assigns a PDSCH resource for (user) data within the same subframe. The PDCCH control channel region within a subframe consists of a set of CCE where the total number of CCEs in the control region of subframe is distributed throughout time and frequency control resource. Multiple CCEs can be combined to effectively reduce the coding rate of the control channel. CCEs are combined in a predetermined manner using a tree structure to achieve different coding rate.
On a transport channel level, the information transmitted via the PDCCH is also referred to as L1/L2 control signaling (for details on L1/L2 control signaling see above).
Enhanced-PDCCH
The Enhanced PDCCH (EPDCCH) is transmitted based on UE-specific reference signals. In order to efficiently use UE-specific reference signals, the mapping of Enhanced-PDCCH is allocated in the PDSCH region. In order not to blind-decode the whole bandwidth, the search space of EPDCCH would be limited within a set of PRB pairs. The set of PRB pairs can be first configured by higher layer signaling, or at least is assumed to be known by the receiver prior to trying to detect any EPDCCH.
The EPDCCH consists of an aggregation of one or more Enhanced Control Channel Elements (ECCEs). Furthermore, an ECCE is formed from resource element groups that are mapped to resource elements in the time/frequency grid, called Enhanced Resource Element Groups (EREGs).
Time Division Duplex—TDD
LTE can operate in Frequency-Division-Duplex (FDD) and Time-Division-Duplex (TDD) modes in a harmonized framework, designed also to support the evolution of TD-SCDMA (Time-Division Synchronous Code Division Multiple Access). TDD separates the uplink and downlink transmissions in the time domain, while the frequency may stay the same.
The term “duplex” refers to bidirectional communication between two devices, distinct from unidirectional communication. In the bidirectional case, transmissions over the link in each direction may take place at the same time (“full duplex”) or at mutually exclusive times (“half duplex”).
For TDD in the unpaired radio spectrum, the basic structure of RBs and REs is depicted in FIG. 4, but only a subset of the subframes of a radio frame are available for downlink transmissions; the remaining subframes are used for uplink transmissions, or for special subframes. Special subframes are important to allow uplink transmission timings to be advanced, so as to make sure that transmitted signals from the UEs (i.e. uplink) arrive roughly at the same time at the eNodeB. Since the signal propagation delay is related to the distance between transmitter and receiver (neglecting reflection and other similar effects), this means that a signal transmitted by a UE near the eNodeB travels for a short time than the signals transmitted by a UE far from the eNodeB. In order to arrive at the same time, the far UE has to transmit its signal earlier than the near UE, which is solved by the so-called “timing advance” procedure in 3GPP systems. In TDD this has the additional circumstance that the transmission and reception occur on the same carrier frequency, i.e. downlink and uplink need to be duplexed in time domain. While a UE far from the eNodeB needs to start uplink transmission earlier than the near UE, conversely, a downlink signal is received by a near UE earlier than by the far UE. In order to be able to switch the circuitry from DL reception to UL transmission, guard time is defined in the special subframe. To additionally take care of the timing advance problem, the guard time for a far UE needs to be longer than for a near UE.
This TDD structure is known as “Frame Structure Type 2” in 3GPP LTE Release 8 and later, of which seven different uplink-downlink configurations are defined, which allow a variety of downlink-uplink ratios and switching periodicities. FIG. 5 illustrates the Table with the 7 different TDD uplink-downlink configurations, indexed from 0-6, where “D” shall indicate a downlink subframe, “U” an uplink subframe and “S” a special subframe. As can be seen therefrom, the seven available TDD uplink-downlink configurations can provide between 40% and 90% of downlink subframes (when, for simplicity, counting a special subframe as a downlink subframe, since part of such a subframe is available for downlink transmission).
FIG. 6 shows the frame structure type 2, particularly for a 5 ms switch-point periodicity, i.e. for TDD configurations 0, 1, 2 and 6.
FIG. 6 illustrates a radio frame, being 10 ms in length, and the corresponding two half-frames of 5 ms each. The radio frame consists of 10 subframes with each 1 ms, where each of the subframes is assigned the type of uplink, downlink or special, as defined by one of the Uplink-downlink configurations according to the table of FIG. 5.
As can be appreciated from FIG. 5, subframe #1 is always a Special subframe, and subframe #6 is a Special subframe for TDD configurations 0, 1, 2 and 6; for TDD configurations 3, 4 and 5, subframe #6 is destined for downlink. Special subframes include three fields: DwPTS (Downlink Pilot Time Slot), the GP (Guard Period) and UpPTS (Uplink Pilot Time Slot).
The TDD configuration applied in the system has an impact on many operations performed at the mobile station and base station, such as radio resource management (RRM) measurements, channel state information (CSI) measurements, channel estimations, PDCCH detection and HARQ timings.
In particular, the UE reads the system information to learn about the TDD configuration in its current cell, i.e. which subframe to monitor for measurement, for CSI measure and report, for time domain filtering to get channel estimation, for PDCCH detection, or for UL/DL ACK/NACK feedback.
Shortcoming of Current Semi-Static TDD UL/DL Configuration Scheme
Currently, LTE TDD allows for asymmetric UL-DL allocations by providing seven different semi-statically configured uplink-downlink configurations, denoted static TDD configurations in the following (see FIG. 5). The current mechanism for adapting UL-DL allocation is based on the system information acquisition procedure or the system information change procedure, where the particular static UL-DL TDD configuration is indicated by a SIB, particularly by the TDD-config parameter in SIB1 (for details on the broadcast of system information, 3GPP TS 36.331, v11.4.0, incorporated herein by reference).
With the Release 8 system information change procedure, the supported time scale for a TDD UL/DL re-configuration is every 640 ms or larger. When re-using the ETWS (Earthquake and Tsunami Warning System), the supported time scale for UL-DL TDD re-configuration is every 320 ms or larger depending on the configured default paging cycle.
The semi-static allocation of the TDD UL/DL configuration may or may not match the instantaneous traffic situation. The time scale to change the static TDD configuration is rather large. It would be advantageous to adapt more quickly the TDD UL/DL configuration to the current traffic needs; for instance, in order to dynamically create more downlink subframes to increase downlink bandwidth or in order to dynamically create more blank uplink subframes to mitigate interference to the communication e.g. in uplink or downlink of a neighbouring cell. Correspondingly, it is expected that Release 12 will adopt a more dynamic change of the TDD UL/DL configuration.
3GPP launched a study item TR 36.828 v11.0.0 to study the time scales of various types of TDD UL/DL re-configurations and their benefits and disadvantages. In general, the study item concluded that faster TDD UL/DL re-configuration time scales provide larger benefits than slower TDD UL/DL re-configuration time scales. Further, the amount of required specification changes varies depending on the supported re-configuration time scales.
Need for a Faster TDD UL/DL Configuration Scheme
Recently the reconfiguration of the TDD value has been under close scrutiny. The tendency is to reconfigure the TDD more often than previously, so as to better adapt to changing channel and traffic conditions.
A rough value for the interval between TDD changes can be, for example, in the range from 10 ms to 640 ms. Moreover, the change of TDD must usually be notified to a plurality of UEs.
These two requirements make the notification of the changing TDD rather complex. While a message for each UE would result in each UE being constantly informed about the new TDD value, such an approach increases the amount of DCI information on the channel, with a direct reduction in terms of available data capacity. Conversely, the use of a broadcast message, which would not have such a large DCI overhead, is not suitable as its frequency is too small to keep up with the intended frequency change of the TDD.
One of the objects of the present invention is to allow a frequent transmission of the TDD reconfiguration value to a number of UEs. A more general objective of the present invention is to transmit any payload which needs to reach several UEs with such requirements that make a broadcasting message unsuitable.
This is achieved by the teaching of the independent claims.
In particular, an embodiment of the present invention can relate to a method for determining resources for control channel transmission, including the step of storing a configurable Radio Network Temporary Identifier in a first User Equipment as well as in a second User Equipment in the same cell of the first User Equipment, wherein the configurable Radio Network Temporary Identifier has the same value for the first User Equipment and for the second User Equipment and wherein the configurable Radio Network Temporary Identifier is configured to define a common search space in an Enhanced Physical Downlink Control Channel for the first User Equipment and for the second User Equipment.
In some embodiments, the value of the configurable Radio Network Temporary Identifier is a fixed value, in particular 0, or it is computed based on any value associated with the cell detection procedure, in particular the Physical Cell ID, and/or based on a value conveyed by a Master Information Block, and/or based on the value of a Physical Broadcast Channel, and/or based on the value of a Radio Resource Control information element.
In some embodiments, the value of the configurable Radio Network Temporary Identifier is equal to the Physical Cell ID plus 1.
Some embodiments are further comprising the step of transmitting data to the first and/or second User Equipment based on the value of the configurable Radio Network Temporary Identifier.
In some embodiments, the step of transmitting data comprises the step of mapping the data to one or more Enhanced Control Channel Element defined based on the value of the configurable Radio Network Temporary Identifier.
In some embodiments, the step of transmitting data comprises the step of adding a Cyclic Redundancy Check code to the data, and wherein the Cyclic Redundancy Check code is masked by using the configurable Radio Network Temporary Identifier, in particular by a binary XOR operation of the Cyclic Redundancy Check code with the configurable Radio Network Temporary Identifier.
In some embodiments, the step of transmitting data comprises the step of adding a Cyclic Redundancy Check code to the data, and wherein the Cyclic Redundancy Check code is masked by using a Cell Radio Network Temporary Identifier, in particular by a binary XOR operation of the Cyclic Redundancy Check code with a Cell Radio Network Temporary Identifier.
In some embodiments, the configurable Radio Network Temporary Identifier is used for the mapping of high aggregation levels, in particular for the two highest available aggregation levels, and wherein the configurable Radio Network Temporary Identifier is not used for the mapping of at least one of the remaining aggregation levels.
In some embodiments, two distributed Enhanced Physical Downlink Control Channel-Physical Resource Block sets are used and the first set of the two Enhanced Physical Downlink Control Channel-Physical Resource Block sets offers more high aggregation level candidates than the second set of the two distributed Enhanced Physical Downlink Control Channel-Physical Resource Block sets, and wherein the configurable Radio Network Temporary Identifier is used for the mapping of only the first set of the two distributed Enhanced Physical Downlink Control Channel-Physical Resource Block sets.
In some embodiments, one distributed Enhanced Physical Downlink Control Channel-Physical Resource Block set and one localized Enhanced Physical Downlink Control Channel-Physical Resource Block set are used, and wherein the configurable Radio Network Temporary Identifier is used for the mapping of only the distributed Enhanced Physical Downlink Control Channel-Physical Resource Block set.
In some embodiments, the configurable Radio Network Temporary Identifier is used for the mapping of low aggregation levels, in particular for the two lowest available aggregation levels and wherein the configurable Radio Network Temporary Identifier is not used for the mapping of at least one of the remaining aggregation levels.
In some embodiments, two distributed Enhanced Physical Downlink Control Channel-Physical Resource Block sets are used and the second set of the two Enhanced Physical Downlink Control Channel-Physical Resource Block sets offers more low aggregation level candidates than the first set of the two distributed Enhanced Physical Downlink Control Channel-Physical Resource Block sets, and wherein the configurable Radio Network Temporary Identifier is used for the mapping of only the second set of the distributed two Enhanced Physical Downlink Control Channel-Physical Resource Block sets.
In some embodiments, one distributed Enhanced Physical Downlink Control Channel-Physical Resource Block set and one localized Enhanced Physical Downlink Control Channel-Physical Resource Block set are used, and wherein the configurable Radio Network Temporary Identifier is used for the mapping of only the localized Enhanced Physical Downlink Control Channel-Physical Resource Block set.
In some embodiments, the data defines a Time Division Duplex uplink/downlink configuration value for the communication between a transmitter and the first User Equipment and/or the second User Equipment.
In some embodiments, the data is transmitted in fixed downlink subframes only, in particular in subframe 0 and in subframe 5, of a radio frame.
In some embodiments, a Cell Radio Network Temporary Identifier is used for mapping the data to one or more Enhanced Control Channel Element in the remaining subframes of a radio frame.
In some embodiments, three Enhanced Physical Downlink Control Channel-Physical Resource Block sets are available and the configurable Radio Network Temporary Identifier is used for the mapping of only one of the three Enhanced Physical Downlink Control Channel-Physical Resource Block sets.
Further, an embodiment of the present invention can relate to a transmitter configured to use a configurable Radio Network Temporary Identifier for determining resources for control channel transmission in order to define a common search space in an Enhanced Physical Downlink Control Channel for a first User Equipment and for a second User Equipment in the same cell of the first User Equipment.
In some embodiments, the value of the configurable Radio Network Temporary Identifier is a fixed value, in particular 0, or it is computed based on any value associated with the cell detection procedure, in particular the Physical Cell ID, and/or based on the value of a Master Information Block, and/or based on the value of a Physical Broadcast Channel, and/or based on the value of a Radio Resource Control.
In some embodiments, the value of the configurable Radio Network Temporary Identifier is equal to the Physical Cell ID plus 1.
Some embodiments are further configured to transmit data to the first and/or second User Equipment based on the value of the configurable Radio Network Temporary Identifier.
In some embodiments, for the transmission of the data the transmitter is further configured to map the data to one or more Enhanced Control Channel Element defined based on the value of the configurable Radio Network Temporary Identifier.
In some embodiments, for the transmission of the data the transmitter is further configured to add a Cyclic Redundancy Check code to the data, and wherein the Cyclic Redundancy Check code is masked by using the configurable Radio Network Temporary Identifier, in particular by a binary XOR operation of the Cyclic Redundancy Check code with the configurable Radio Network Temporary Identifier.
In some embodiments, for the transmission of the data the transmitter is further configured to add a Cyclic Redundancy Check code to the transmitted data, and wherein the Cyclic Redundancy Check code is masked by using a Cell Radio Network Temporary Identifier, in particular by a binary XOR operation of the Cyclic Redundancy Check code with a Cell Radio Network Temporary Identifier.
In some embodiments, the transmitter is configured to use the configurable Radio Network Temporary Identifier for the mapping of high aggregation levels, in particular for the two highest available aggregation levels, and wherein transmitter is configured not to use the configurable Radio Network Temporary Identifier for the mapping of at least one of the remaining aggregation levels.
In some embodiments, the transmitter is configured to use two distributed Enhanced Physical Downlink Control Channel-Physical Resource Block sets and the first set of the two Enhanced Physical Downlink Control Channel-Physical Resource Block sets offers more high aggregation level candidates than the second set of the two distributed Enhanced Physical Downlink Control Channel-Physical Resource Block sets, and wherein the transmitter is configured to use the configurable Radio Network Temporary Identifier for the mapping of only the first set of the two distributed Enhanced Physical Downlink Control Channel-Physical Resource Block sets.
In some embodiments, the transmitter is configured to use one distributed Enhanced Physical Downlink Control Channel-Physical Resource Block set and one localized Enhanced Physical Downlink Control Channel-Physical Resource Block set, and wherein the transmitter is configured to use the configurable Radio Network Temporary Identifier for the mapping of only the distributed Enhanced Physical Downlink Control Channel-Physical Resource Block set.
In some embodiments, the transmitter is configured to use the configurable Radio Network Temporary Identifier for the mapping of low aggregation levels, in particular for the two lowest available aggregation levels and wherein the transmitter is configured not to use the configurable Radio Network Temporary Identifier for the mapping of at least one of the remaining aggregation levels.
In some embodiments, the transmitter is configured to use two distributed Enhanced Physical Downlink Control Channel-Physical Resource Block sets and the second set of the two Enhanced Physical Downlink Control Channel-Physical Resource Block sets offers more low aggregation level candidates than the first set of the two distributed Enhanced Physical Downlink Control Channel-Physical Resource Block sets, and wherein the transmitter is configured to use the configurable Radio Network Temporary Identifier for the mapping of only the second set of the distributed two Enhanced Physical Downlink Control Channel-Physical Resource Block sets.
In some embodiments, the transmitter is configured to use one distributed Enhanced Physical Downlink Control Channel-Physical Resource Block set and one localized Enhanced Physical Downlink Control Channel-Physical Resource Block set, and wherein the transmitter is configured to use the configurable Radio Network Temporary Identifier for the mapping of only the localized Enhanced Physical Downlink Control Channel-Physical Resource Block set.
In some embodiments, the data defines a Time Division Duplex value for the communication between the transmitter and the first User Equipment and/or the second User Equipment.
In some embodiments, the transmitter is configured to transmit data in fixed download subframes only, in particular in subframe 0 and in subframe 5.
In some embodiments, the transmitter is configured to use a Cell Radio Network Temporary Identifier to transmit data in the remaining subframes.
In some embodiments, the transmitter is configured to use three Enhanced Physical Downlink Control Channel-Physical Resource Block sets and wherein the transmitter is configured to use the configurable Radio Network Temporary Identifier for the mapping of only one of the three Enhanced Physical Downlink Control Channel-Physical Resource Block sets.
Further, an embodiment of the present invention can further relate to a method for determining resources for control channel reception including the step of storing a configurable Radio Network Temporary Identifier in a first User Equipment, wherein the configurable Radio Network Temporary Identifier is used by the User Equipment to define a search space common to the first User Equipment and to a second User Equipment, in the same cell of the first User Equipment, in an Enhanced Physical Downlink Control Channel.
In some embodiments, wherein the value of the configurable Radio Network Temporary Identifier is a fixed value, in particular 0, or it is computed based on any value associated with the cell detection procedure, in particular the Physical Cell ID, and/or based on the value of a Master Information Block, and/or based on the value of a Physical Broadcast Channel, and/or based on the value of a Radio Resource Control.
In some embodiments, wherein the value of the configurable Radio Network Temporary Identifier is equal to the Physical Cell ID plus 1.
Some embodiments are further comprising the step of receiving data based on the value of the configurable Radio Network Temporary Identifier.
In some embodiments, the step of receiving data comprises the step of blind decoding data from one or more Enhanced Control Channel Element defined based on the value of the configurable Radio Network Temporary Identifier.
In some embodiments, the step of receiving data comprises the step of checking a Cyclic Redundancy Check code by using the configurable Radio Network Temporary Identifier, in particular by a binary XOR operation of the Cyclic Redundancy Check code with the configurable Radio Network Temporary Identifier.
In some embodiments, the step of receiving data comprises the step of checking a Cyclic Redundancy Check code by using a Cell Radio Network Temporary Identifier, in particular by a binary XOR operation of the Cyclic Redundancy Check code with a Cell Radio Network Temporary Identifier.
In some embodiments, the configurable Radio Network Temporary Identifier is used for the search space definition of high aggregation levels, in particular for the two highest available aggregation levels, and wherein the configurable Radio Network Temporary Identifier is not used for the search space definition of at least one of the remaining aggregation levels.
In some embodiments, two distributed Enhanced Physical Downlink Control Channel-Physical Resource Block sets are used and the first set of the two Enhanced Physical Downlink Control Channel-Physical Resource Block sets offers more high aggregation level candidates than the second set of the two distributed Enhanced Physical Downlink Control Channel-Physical Resource Block sets, and wherein the configurable Radio Network Temporary Identifier is used for the search space definition of only the first set of the two distributed Enhanced Physical Downlink Control Channel-Physical Resource Block sets.
In some embodiments, one distributed Enhanced Physical Downlink Control Channel-Physical Resource Block set and one localized Enhanced Physical Downlink Control Channel-Physical Resource Block set are used, and wherein the configurable Radio Network Temporary Identifier is used for the search space definition of only the distributed Enhanced Physical Downlink Control Channel-Physical Resource Block set.
In some embodiments, the configurable Radio Network Temporary Identifier is used for the search space definition of low aggregation levels, in particular for the two lowest available aggregation levels, and wherein the configurable Radio Network Temporary Identifier is not used for the search space definition of at least one of the remaining aggregation levels.
In some embodiments, two distributed Enhanced Physical Downlink Control Channel-Physical Resource Block sets are used and the second set of the two Enhanced Physical Downlink Control Channel-Physical Resource Block sets offers more low aggregation level candidates than the first set of the two distributed Enhanced Physical Downlink Control Channel-Physical Resource Block sets, and wherein the configurable Radio Network Temporary Identifier is used for the search space definition of only the second set of the distributed two Enhanced Physical Downlink Control Channel-Physical Resource Block sets.
In some embodiments, one distributed Enhanced Physical Downlink Control Channel-Physical Resource Block set and one localized Enhanced Physical Downlink Control Channel-Physical Resource Block set are used, and wherein the configurable Radio Network Temporary Identifier is used for the search space definition of only the localized Enhanced Physical Downlink Control Channel-Physical Resource Block set.
In some embodiments, the data defines a Time Division Duplex value for the communication between a transmitter and the first User Equipment.
In some embodiments, the data is received in fixed download subframes only, in particular in subframe 0 and in subframe 5.
In some embodiments, a Cell Radio Network Temporary Identifier is used for the reception of data in the remaining subframes.
In some embodiments, three Enhanced Physical Downlink Control Channel-Physical Resource Block sets are available and the configurable Radio Network Temporary Identifier is used for the search space definition of only one of the three Enhanced Physical Downlink Control Channel-Physical Resource Block sets.
Further, an embodiment of the invention can relate to a User Equipment configured to store a configurable Radio Network Temporary Identifier, wherein the configurable Radio Network Temporary Identifier is used by the User Equipment to define a search space common to the User Equipment and to a second User Equipment, in the same cell of the User Equipment, in an Enhanced Physical Downlink Control Channel.
In some embodiments, the value of the configurable Radio Network Temporary Identifier is a fixed value, in particular 0, or it is computed based on any value associated with the cell detection procedure, in particular the Physical Cell ID, and/or based on the value of a Master Information Block, and/or based on the value of a Physical Broadcast Channel, and/or based on the value of a Radio Resource Control.
In some embodiments, the value of the configurable Radio Network Temporary Identifier is equal to the Physical Cell ID plus 1.
In some embodiments, the User Equipment is further configured to receive data based on the value of the configurable Radio Network Temporary Identifier.
In some embodiments, the User Equipment is configured to blind decode data from one or more Enhanced Control Channel Element defined based on the value of the configurable Radio Network Temporary Identifier.
In some embodiments, the User Equipment is configured to check a Cyclic Redundancy Check code by using the configurable Radio Network Temporary Identifier, in particular by a binary XOR operation of the Cyclic Redundancy Check code with the configurable Radio Network Temporary Identifier.
In some embodiments, the User Equipment is configured to check a Cyclic Redundancy Check code by using a Cell Radio Network Temporary Identifier, in particular by a binary XOR operation of the Cyclic Redundancy Check code with a Cell Radio Network Temporary Identifier.
In some embodiments, the User Equipment is configured to use the configurable Radio Network Temporary Identifier for the search space definition of high aggregation levels, in particular for the two highest available aggregation levels and wherein the User Equipment is configured not to use the configurable Radio Network Temporary Identifier for the search space definition of at least one of the remaining aggregation levels.
In some embodiments, two distributed Enhanced Physical Downlink Control Channel-Physical Resource Block sets are used and the first set of the two Enhanced Physical Downlink Control Channel-Physical Resource Block sets offers more high aggregation level candidates than the second set of the two distributed Enhanced Physical Downlink Control Channel-Physical Resource Block sets, and wherein the User Equipment is configured to use the configurable Radio Network Temporary Identifier for the search space definition of only the first set of the two distributed Enhanced Physical Downlink Control Channel-Physical Resource Block sets.
In some embodiments, one distributed Enhanced Physical Downlink Control Channel-Physical Resource Block set and one localized Enhanced Physical Downlink Control Channel-Physical Resource Block set are used, and wherein the User Equipment is configured to use the configurable Radio Network Temporary Identifier for the search space definition of only the distributed Enhanced Physical Downlink Control Channel-Physical Resource Block set.
In some embodiments, the User Equipment is configured to use the configurable Radio Network Temporary Identifier only for the search space definition of low aggregation levels, in particular for the two lowest available aggregation levels, and wherein the User Equipment is configured not to use the configurable Radio Network Temporary Identifier for the search space definition of at least one of the remaining aggregation levels.
In some embodiments, two distributed Enhanced Physical Downlink Control Channel-Physical Resource Block sets are used and the second set of the two Enhanced Physical Downlink Control Channel-Physical Resource Block sets offers more low aggregation level candidates than the first set of the two distributed Enhanced Physical Downlink Control Channel-Physical Resource Block sets, and wherein the User Equipment is configured to use the configurable Radio Network Temporary Identifier for the search space definition of only the second set of the distributed two Enhanced Physical Downlink Control Channel-Physical Resource Block sets.
In some embodiments, one distributed Enhanced Physical Downlink Control Channel-Physical Resource Block set and one localized Enhanced Physical Downlink Control Channel-Physical Resource Block set are used, and wherein the User Equipment is configured to use the configurable Radio Network Temporary Identifier for the search space definition of only the localized Enhanced Physical Downlink Control Channel-Physical Resource Block set.
In some embodiments, the data defines a Time Division Duplex value for the communication between a transmitter and the User Equipment.
In some embodiments, the User Equipment is configured to receive the data in fixed download subframes only, in particular in subframe 0 and in subframe 5.
In some embodiments, the User Equipment is configured to use a Cell Radio Network Temporary Identifier for the reception of data in the remaining subframes.
In some embodiments, three Enhanced Physical Downlink Control Channel-Physical Resource Block sets are available and the User Equipment is configured to use the configurable Radio Network Temporary Identifier for the search space definition of only one of the three Enhanced Physical Downlink Control Channel-Physical Resource Block sets.